1. Field of the Invention
The present invention relates to the synthesis of 3-benzylthio-2-alkylpropionic acids and their derivatives.
2. Description of the Prior Art
3-benzylthio-2-methylpropionic acids are important intermediates for the synthesis of captopril and alacepril, orally active inhibitors of angiotension converting enzymes used in treating hypertension and cardiac failure.
A method for preparing 3-benzylthio-2-methylpropionic acids and their derivatives has been disclosed in Candian patent No. 1,103,256. Said method includes adding p-methoxy-.alpha.-toluene thiol to an aqueous solution of methacrylic acid in NaOH, followed by heating on a steam bath. The yield of the product, 3-[{4-methoxyphenyl)methylthio]-2-methylpropionic acid was reported as 23%. Accordingly, a method for preparing 3-benzylthio-2-methylpropionic acids in high yield is needed in the art.